Received: 7 July 2018
Accepted: 25 June 2019
First Online: 28 June 2019
Ethics approval and consent to participate
: Ethical approval was obtained from the Human Research Ethics Committee of Thammasat University (Institutional Review Board no. 045/2560). The committee waived the need for written informed consent because responding to this anonymized questionnaire contained no more than minimal risk and consent by action was used.
: Not applicable.
: The authors declare that they have no competing interests.